The Oneplus 3T can accept dual SIMs. That is a HUGE plus for a world traveler such as me. One tray holds my world roamer SIM (Truphone or Piranha) and leaves the other for any in-country SIMs that might be a better value. Or you can use two SIMs with different preferred roaming lists - like Piranha and Truphone. Anyway it's a convenience I would not want to travel without.